If you do not see Insight Timer in the Health section under your iOS settings, please logout of the app, reboot your device and login again.
To enable Apple Health please check the following settings and see attached screenshots.
1. Open Insight Timer > Select Profile icon > Gear icon > Apple Health.
2. Launch iOS settings - Privacy > Health > Ensure Insight Timer is selected.
You may also want to ensure you iOS software is up to date.